Many different types of products utilize compressed gas. In some cases compressed gas may be used to actuate equipment, for example pneumatic hand tools. In other cases compressed gas is used to alter a product, for example compressed carbon dioxide (CO2) is used to carbonate soft drinks. In these cases the gas is supplied from a pressurized canister or cylinder.
Gas from a canister can also be used to drive a tool, for example the nail driver described in copending application Ser. No. 10/846,547 filed May 17, 2004 by Patrick, which is incorporated herein by reference. Typically such an application would utilize gas pressurized by a compressor, which is supplied at a relatively high pressure. In this type of application carbon dioxide (CO2) can advantageously be used because in its gaseous state carbon dioxide is non-flammable, colourless and odourless, and can be supplied at the high pressures needed to drive a pneumatic tool. Carbon dioxide (CO2) is unusual, however, because it solidifies directly from its gaseous state at −109° F. (−70° C.) at atmospheric pressure.
Carbon dioxide can be supplied as a gas from an external source to a sealed enclosure, from the solid phase (colloquially known as “dry ice”), but is normally supplied from the liquid phase. Liquid CO2 cannot exist unless it is colder than 87.4° F. (30.8° C.) and under a pressure of at least 60.4 psig. Conditions in liquid CO2 tanks are usually about 0° F. (−18° C.) and 126 psig. Liquid CO2 is stored in pressurized cylinders, and changes to a gas when released from the cylinder, producing 0.5 cubic meters of gas per kilogram of liquid CO2.
As is typical of compressed gas applications, the rate of release of CO2 gas from a pressurized CO2 cylinder is controlled by a regulator. However, because of the unique properties of carbon dioxide, as liquid CO2 turns into gas it cools drastically as the pressure of the CO2 is reduced across the regulator. This cooling can be so severe as to freeze the regulator orifices, restricting or in the worst case stopping the gas flow. Thus, carbon dioxide frequently causes ordinary regulators to become blocked with solid phase CO2, due to the dramatic cooling effect that occurs when the gas pressure is reduced as it is dispensed.
Electrically heated regulators have been employed successfully to keep the CO2 gas and the regulator from freezing. However, this solution requires electrical power, which involves additional cost and limits the environments in which the regulator can be used.
It would accordingly be advantageous to have a CO2 pressure regulator that does not freeze when CO2 gas is released, without requiring the application of heat from an external source.